alt Hacker NewsCloud applications can do nil, because the api for the background transfers is only working for iCloud, Nextcloud and other apps in the background get a couple of kb/s effectively pushing you to pay apple. Great Dark pattern from Apple that has been going on for years.
I’ve heard this admonishment from the developer community, but I haven’t run into this issue myself. I expect there is some kind of dynamic at play rather than a strict hard and fast rule in the OS.
I’ve got multiple independent apps that do background sync to various destinations and I’ve never had any problems. Depending on how much data and processing is needed for a sync, sometimes they do get stopped by the OS, especially when on battery power, but they resume when the app is opened. This hasn’t been a big issue for me.
Almost all of the problems I’ve had with this kind of workload have been specific to the OneDrive app, and it doesn’t seem to matter whether it’s a SPO/business or MSA/personal account, or whether via the Files app or native app UI.